Mechanical trigger arrangement

ABSTRACT

The present invention relates to an arrangement for the repeated mechanical triggering of various types of downhole equipment, the arrangement comprising a spring element ( 4 ) and a string section ( 1 ). The invention is characterized in that the arrangement comprises a rotary sleeve ( 7 ), with turning faces ( 1′, 1″; 2′, 2″ ) being provided between the string section ( 1 ) and the rotary sleeve ( 7 ), one set of the turning faces ( 1′, 1″ ) having an equivalent slope and the other set of turning faces ( 2′, 2″ ) having a different slope, the arrangement being configured to force a relative rotary movement between the string section ( 1 ) and the rotary sleeve ( 7 ) as a premise for an axial movement, with the amount of rotary movement of the rotary sleeve ( 7 ) depending on the force being applied to the arrangement, the stiffness of spring ( 4 ), as well as the slope of the turning faces ( 1\1″; 2′, 2″ ), the arrangement being configured to release the energy stored therein when the rotary sleeve ( 7 ) has been rotated by an amount causing the abutment face ( 3″ ) of the rotary sleeve ( 7 ) to no longer be axially abutted against the abutment face ( 3′ ) of an end piece ( 6 ), whereupon the rotary sleeve ( 5 ) and the string section ( 1 ) will be displaced relative to the end piece ( 6 ) allowing the spring ( 4 ) to release its stored energy.

The present invention relates to a mechanical trigger arrangement for the repeated mechanical triggering of various types of downhole equipment, such as the repeated triggering of impact hammers, for example, for which a predetermined resistance against movement is needed in order to tension a tensioning mechanism, such as a spring mechanism, also referred to as an accelerator, for the purpose of storing potential energy that may be subsequently released and converted into kinetic energy.

Frequently, when drilling or intervention tools become stuck in an oil or gas well, there will be a need to be able to apply impact energy to the stuck equipment for the release thereof. For this purpose, impact hammers are used. One type of impact hammers is tensioned using a wireline, wherein the alternate pulling and slackening of the wireline will cause a desired number of repeated blows against the stuck equipment to which the impact hammer has been attached.

Several types of downhole impact hammers exist; mechanical, hydraulic, and mechanical-hydraulic. A common feature of such impact hammers is that they are tensioned and subsequently released/triggered for delivering a blow.

In essence, impact hammers consist of an inner string section and an outer pipe section being telescopically connected so as to allow for a relative axial movement between the sections. In the end position, the string section and pipe section meet in an impact, so that the relative kinetic energy between the sections is transferred in the form of impact energy.

A trigger mechanism will ensure that the relative movement of the inner string section and outer pipe section is delayed or reduced by applying an axial force until the tensioning has reached a certain level. In this manner, potential energy may be stored in a suitable spring, for example. When the trigger mechanism is subsequently released, the stored energy is converted into kinetic energy by the initiation of the relative movement between the inner string section and outer pipe section.

The trigger mechanism of a mechanical impact hammer typically includes a spring element resisting the movement of the inner string section relative to the outer pipe section. The spring element is connected to a locking means that is released at a predetermined position, which position is reached by forcing a sufficient compression of the spring element. On the application of a sufficient load to the impact hammer, the locking means is released and the stored energy will be converted into kinetic energy, after which the sections ultimately meet in an impact.

U.S. Pat. No, 3,685,598 relates to an impact hammer that may adjusted to a desired release force. The impact hammer of U.S. Pat. No. 3,685,598 includes a mandrel being telescopically arranged in a housing, with locking means being provided retaining the mandrel in a fixed position relative to the housing until a longitudinal force of sufficient magnitude is applied to the impact hammer. The longitudinal force is counteracted by way of an elastic element, the resisting force of which is a function of the longitudinal movement required to release the locking means. The impact hammer also includes adjustable elements that may be used for adjusting the amount of longitudinal movement of the elastic elements required to release the locking means and hence trigger the impact hammer.

Several variants of mechanisms that effect movement delay and thereby allow for the tensioning of an accelerator exist, with such mechanisms being either hydraulically or mechanically actuated. In general, hydraulic tensioning mechanisms are more expensive to manufacture, and are less suitable at high operational temperatures as the properties of the hydraulic fluid is affected by higher temperatures.

The present invention provides a mechanical trigger arrangement, which, as compared to corresponding hydraulic arrangements, makes a highly operationally reliable and economically advantageous alternative, as the mechanical trigger arrangement of the present invention provides a simple and robust design being comprised of only a few moveable parts. Thus, the arrangement according to the present invention results in a simplified manufacturing process, making the trigger arrangement an economically, alternative product that may be used in various applications for which economical factors are essential.

The present invention also allows for downhole operations involving the use of very high suspended loads, as the release force of the mechanical trigger arrangement may be adjusted to the necessary level, i.e. the mechanical trigger arrangement will not be released without the existence of a predetermined excessive load in addition to the suspended load. Moreover, the arrangement according to the present invention has the advantage over the conventional trigger arrangements that it may be adjusted to release at a predetermined trigger force with a much greater accuracy as the trigger force will depend directly on a spring device being compressed and released, without any significant influence from conditions like friction and wear.

As compared with the prior art, the present invention provides a mechanical trigger arrangement differing significantly from the conventional solutions and offering significant advantages with respect to operation, efficiency, reliability, and economy.

The mechanical trigger arrangement according to the present invention is configured for having a resistance against an axial movement of a protruding string section for applied forces up to a predetermined magnitude, beyond which the resistance against further movement is very small.

In the following, a detailed description of an embodiment of the present invention is given, with reference to the accompanying drawings, in which:

FIG. 1 shows the arrangement in the start position thereof,

FIG. 2 shows the arrangement in the maximum tensioned position thereof,

FIG. 3 shows the arrangement in the released position thereof,

FIG. 4 shows the arrangement in a return position thereof,

FIGS. 5 and 6 show the string section of the arrangement in different angle views,

FIG. 7 shows the string section of FIGS. 5 and 6, as seen in an end view,

FIG. 8 shows section A of FIG. 5,

FIGS. 9-11 show an end piece comprising a beak in different angle views, and

FIGS. 12-15 show a rotary sleeve in different angle views.

The mechanical trigger arrangement according to the present invention is configured to force a relative rotary movement between the two moveable parts (string section 1 and rotary sleeve 7) of the trigger arrangement as a premise for the axial movement. The rotary sleeve 7 is adapted for engaging one of the turning faces 1′, 2′ of string section 1, the position of turning faces 1′, 2′ being dependent on the axial position of rotary sleeve 7 relative to string section 1. The turning faces of string section 1 and the corresponding turning faces of rotary sleeve 7 have different slopes, with 1′ and 1″ having an equivalent slope and 2′ and 2″ having an equivalent slope.

Turning faces 1′ and 1″ has the least slope. The purpose of these turning faces is to rotate the rotary sleeve to an unlocked position. The small slope ensures that a high magnitude force is developed.

Turning faces 2′ and 2″ have a greater slope. The purpose of these turning faces is to have the residual tension of the coil spring rotate the sleeve back to the starting position to allow the mechanical trigger arrangement to be re-tensioned for the next triggering cycle.

String section 1 is rotationally supported in an end piece 6 comprising a beak 8 in order to achieve a certain mutual starting orientation/position between the end piece 6, string section 1, and rotary sleeve 7.

A spring element 4 is disposed between string section 1 and end piece 6 in such a manner that the spring 4 is compressed by the axial movement of string section 1 relative to end piece 6. As can be seen in FIG. 3, the tool is tensioned when string section 1 is pulled to the right. The amount of tensioning of the spring corresponds to the distance with which string section 1 is pulled relative to end piece 6, with turning face 1′ of string section 1 and turning face 1″ of rotary sleeve 7 causing rotary sleeve 7 to rotate relative to the beak 8 of end piece 6 (FIGS. 1 and 2) and ultimately snap into beak 8 as shown in FIG. 3. String section 1 includes a groove 10 ensuring that string section 1 and end piece 6 will not rotate relative to each other, as beak 8 extends into groove 10 (FIG. 10)

As mentioned above, by applying an axial force to string section 1 in the compressive direction of the spring, the interaction of turning faces 1′, 1″ will cause rotary sleeve 7 to rotate or twist. When rotary sleeve 7 then has reached a predetermined/sufficient rotational or twist position, rotary sleeve 7 will no longer be axially resting against the abutment face 3′ of end piece 6 at the end of the beak, whereupon rotary sleeve 7 and string section 1 will be displaced relative to end piece 6 to snap into the beak with no resistance from spring 4. It is at this point the arrangement may be said to perform its trigger function. At the same time, the second set of turning faces 2′, 2″ of string section 1 and rotary sleeve 7, respectively, will come to rest against each other while spring 4 is still somewhat compressed/tensioned. By running string section 1 back in the opposite direction, rotary sleeve 7 will be rotated or twisted back to the starting position by the residual tension of spring 4 and turning faces 2′, 2″, while at the same time rotary sleeve 7 is pushed axially to the right so that abutment face 3″ of rotary sleeve 7 is brought back to the position of axial rest against abutment face 3′ of end piece 6 at the end of the beak, after which the arrangement is ready for the repetition of a new tensioning and release sequence.

The pretension of spring 4 may be adjusted by way of a pretension pin 3 and a spring pretension ring 5. This may be achieved by displacing and locking pretension pin 3 and spring pretension ring 2 axially relative to string section 1. Pretension pin 3 extends into a suitable groove in string section 1. It is understood that other types of pretension elements may also be used, such as a threaded rotatable tensioning disk or a similar element, for example, that increases or reduces the pretension by rotating the disk or similar element up or down along string section 1. 

1-4. (canceled)
 5. An arrangement for repeated mechanical triggering of an impact hammer, the arrangement comprising a string section (1) rotationally restrained and axially movable relative to an end section (96), a rotary sleeve (7) rotatable around the string section (1) and a compressible spring (4) disposed between the end piece (6) and a pre-tension element (3, 5) on the string section (1), characterized in that the rotary sleeve (7) comprises an abutment face (3″) along part of its circumference in a plane perpendicular to its axis of rotation, a first turning face (1″) adapted to a corresponding first turning face (1′) spiral along a first part of the string section (1), a second turning face (2″) adapted to a corresponding second turning face (2′) spiral along a second part of the string section (1), that the rotary sleeve (7) in a first position is oriented such that the abutment face (3″) engages a corresponding abutment face (3′) along part of the circumference of the end piece (6), that the first turning faces (1′, 1″), upon axial displacement of string element (1) towards the end section (6), interact to cause a rotation of the rotary sleeve (7), that the rotary sleeve (7) in a second position is oriented such that the sleeve abutment face (3″) is rotated past the extent of abutment face (3′) on the end piece (6), thereby triggering release of potential energy from the string (4) and providing an impact to the end piece (6), that the rotary sleeve (7) in a third position, axially displaced from the second position, is configured to engage the second turning face (2′) of the string section (1) along the corresponding turning face (2″) on the rotary sleeve (7), and that the second turning faces (2′, 2″), upon being forced together by residual spring force from the spring (4), interact to cause a further rotation of the rotary sleeve (7) back to the first position.
 6. The arrangement of claim 5, characterized in that the string section 1 and rotary sleeve 7 in the released third position, is freely moveable in both axial directions without causing any significant resistance.
 7. The arrangement of claim 6, characterized in that the rotary sleeve 7 in the released third position is freely rotatable around the string section 1 to the first starting position without causing any significant resistance.
 8. The arrangement of claim 5, characterized in that the tensioning resistance of the arrangement is determined by the amount of pretension in the spring, the stiffness of the spring (4), and the slope of the turning faces (1′, 1″; 2′, 2″). 